If you can get measurements of all you plan on having in there might even double it and lay it out on graph paper. Then plan from there. My sewing room is 32 by 18 and it isn't big enough. The long arm takes up half of that and I have 4 other sewing machines set up in there. there is no room for a big layout/cutting table. It started out being the master and bath but I am single so don't need that much room in a bedroom so made it all one room for sewing. couldn't go any bigger wish I could have. Since you do have a chance to get what you will need always go bigger. Remember to take into count your movement around the room and machines while you are sewing.
Lynda